1. Field of Invention
The present invention relates to a hydraulic pump system for an automatic transmission that is configured to minimize a power loss caused by a hydraulic pump.
2. Description of Related Art
For example, a hydraulic pump that is operated by an engine has a suction hole that is connected to an oil fan to supply a discharge hole with pumped oil in a hydraulic pump system for an automatic transmission.
The discharge hole is connected to a high pressure portion (for example, clutch) through a high pressure passage, and a high pressure regulating valve is disposed on a high pressure passage. The high pressure passage supplies a high hydraulic pressure to the high pressure portion. Also, a pressure reduction valve is interposed on the high pressure passage to be connected to a low pressure passage. The low pressure passage supplies a low pressure portion to a low pressure portion (for example, lubrication portion).
The high pressure regulating valve and the pressure reduction valve set a high pressure and a low pressure to recirculate remained oil to a suction hole of the hydraulic pump. Generally, the low pressure portion is used to lubricate an automatic transmission and therefore large amount of oil is necessary and the high pressure portion is used to control a clutch and therefore small amount of oil is necessary.
However, the hydraulic pump pumps entire oil flux base on the high pressure portion and therefore an excessive load is applied to the pump. A durability is deteriorated, a power is lost, and noise and pressure vibration are generated thereby.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.